Secret key algorithms in cryptography
Secret key algorithms also known as symmetric key algorithms use one key that is kept secret by the systems engaged in the encryption and decryption processes.
This single shared key is used for encryption of plain text and decryption of cipher text between sender and receiver.
Some symmetric key algorithms are considered as virtually unbreakable and also these algorithms are very fast.Therefore, secret key algorithms are often used when there is a lot of data needs to be encrypted.
Symmetric key encryption can be either stream ciphers or block ciphers.
Stream ciphers
Stream ciphers encrypt the message bit by bit.
For examples: Caesar cipher and Vigenere cipher
Block ciphers
Block ciphers encrypt the message as a single unit.
For example: Advanced Encryption Standard (AES)
There are hundreds of different symmetric key algorithms available. Each symmetric key algorithm has its own strengths and weaknesses.
More common examples for symmetric key algorithms are DES, 3DES, AES, IDEA, RC4 and RC5.
DES (Data Encryption Standard)
DES was originally developed in 1976 by IBM. It has been one of the most widely used encryption algorithms since it was adopted as the government standard for encryption.
In this standard, the encryption function maps a 64-bit plain text input into 64-bit encrypted output using a 56-bit key.
At the time DES was originally developed, it would have taken hundreds of years to run through all bit combinations of the key(1s and 0s) until we hit the right key. But nowadays, it might only take a day to run through all the possible combinations since nowadays computers are much much faster.
It is the main reason why DES is no longer widely used.
DES is still used in many commercial and other applications for the protection of low-value information.
3DES
As a solution for DES, 3DES involves applying DES three times to each block of data.
3DES is currently considered as the most widely used standard for secure encryption.
We have the option of using the same key for each, the same key for two of the iterations, or a different key for each of the iterations. The most secure implementation is to use a different key for each of the iterations.
Although 3DES gives high protection, it has the drawback of poor performance since it takes more time and resources.
AES (Advanced Encryption Standard)
AES is also referred as Rijndael algorithm since AES actually comes from the Rijndael algorithm.
AES has three ciphers with variable block length and key length as AES-128, AES-192, AES-256.
AES is very fast and very secure.
